a) Field of the Invention
The present invention relates to a method of manufacturing a thin film magnetic head, and, more particularly, to a method of manufacturing an air flow type thin film magnetic head.
b) Description of the Related Art
A thin film magnetic head that performs recording and reproducing of information on and from a magnetic recording medium such as a hard disk includes thin film magnetic head transducers and a slider that mounts them. The slider has air bearing surfaces (ABS) that hold air flow in a space between the magnetic recording medium and ABS, and lift the slider from the medium. When the thin film magnetic head held by an arm is disposed on the surface of a rotating magnetic disk, an air flow sandwiched between the thin film magnetic head and the disk lifts the thin film magnetic head. This type of head is called a magnetic head of the air flow type.
FIG. 6A shows a configuration of a prior art magnetic head of the air flow type. A magnetic head 10 includes a slider 12 and a pair of magnetic head transducers 18 and 20. Each transducer is formed of laminated lagons. On the lower surface of the slider 12, two ABSs 14 and 16 are formed. A region between the two ABSs 14 and 16 is removed to form a groove 30.
FIG. 6B is a schematic perspective view showing a state of the magnetic head in practical use. The magnetic head 10 is disposed above the rotating magnetic disk 22. Dragged by the rotating disk 22, air 13 on the surface of the magnetic disk starts to flow underneath the magnetic head 10. Front portion 16a of the ABS 16 of the slider 12 is inclined and is disposed in tapered relation to the rear portion 16b. The air flow 13 strikes the ABS 16 and glides into a portion underneath the surface. Here, similar air flow is produced underneath the other ABS 14. Thus the slider 12 is subjected to a force in the upward direction shown in the figure and, thereby, lifted from the surface of the magnetic disk. The thin film magnetic transducer 20 performs recording on and reproducing from the magnetic disk from a distance with an amount of lifting H.
FIGS. 7A through 7E shows an example of a method of manufacturing a magnetic head according to a prior art technique, as described above.
As shown in FIG. 7A, a multiplicity of thin film magnetic head transducers 22 are formed on a wafer 21 of ceramic materials such as Al.sub.2 O.sub.3 --TiC. Techniques utilized for the formation are thin film forming technique for manufacturing semiconductor devices, photolithography, patterning technique, and so on.
As shown in FIG. 7B, a multiplicity of grooves are formed on the wafer 21 formed with the multiplicity of thin film magnetic transducers 22. The grooves are cut in orthogonal relation to each other. The grooves prevent chipping that may occur during severing of the wafer 21. Here, a pair of thin film magnetic transducers is disposed on each chip, respectively.
As shown in FIG. 7C, the wafer 21 is severed along the transverse grooves 25 shown in the figure. Each of the severed stripe-shaped pieces of the wafer 21 is called a row 26.
As shown in FIG. 7D, one of the severed surfaces of each row 26 is polished to form an air bearing surface 28. Here, as shown in the figure, the thin film magnetic transducers 22 are formed on a surface perpendicular to the ABS 28.
Then, unnecessary portions of the ABS 28 are removed to form the recessed portions 30. As shown in FIG. 8, rotating blade 32 can be used to remove unnecessary portions 27 and leave the rails 14 and 16. Remaining portions form rails 14 and 16 each of them provided with an air bearing surface. Then, each row 26 is severed along vertical groove 24 to form thin film magnetic heads, as shown in FIG. 7E.
Each of the magnetic heads 10 is necessarily formed with two rails. However, each of the magnetic heads 10 needs one transducer. So, it is not indispensable to form two transducers for each head as shown in the figure. However, in practical use, the magnetic heads 10 are disposed on both sides of the magnetic disk. Thus, it is preferable that each magnetic head have a structure of mirror symmetry.
Consider the case of forming symmetrical rails 14 and 16 on a magnetic head and providing ABS on each of their surfaces as shown in FIG. 7E. Each of the magnetic heads can be used in either side of the magnetic recording medium by forming the thin film magnetic transducers 22 on the back portions of both rails.
The amount of lifting of a magnetic head having parallel rails depends upon relative speed of the head to the rotating magnetic disk. Normally, the amount of lifting increases as the relative speed increases. Consequently, the amount of lifting of the magnetic head depends on the position of the magnetic head with respect to the radial direction of the magnetic disk that is rotating in a fixed rotating speed.
Recently, a demand for a constant amount of lifting of the magnetic head regardless of the relative speed between the magnetic head and the magnetic disk has risen.
FIG. 9 shows an example of a structure of a magnetic head having asymmetrical and non-parallel rails as means for satisfying such demand.
Asymmetrical and non-parallel rails 34 and 36 are formed on the lower surface of the magnetic head 38. Magnetic head transducers 18 and 20 are formed on the back portion of each rail.
It is difficult to form such asymmetrical and non-parallel rails 34 and 36 by machining, as shown in FIG. 8. Therefore, magnetic head having the asymmetrical and non-parallel rails have, so far, been formed by photo-lithography utilizing a mask pattern.
FIGS. 10A through 10F show an example of prior art technique for manufacturing such asymmetrical and non-parallel rails.
As shown in FIG. 10A, rows 26 are formed. Process of forming the rows is similar to the process as shown in FIGS. 7A through 7C. After forming the rows 26, one of the severed side surfaces is polished to form an ABS 28.
As shown in FIG. 10B, the ABS 28 is coated with photoresist material for forming a resist film 40. Here, coating of photoresist material may be substituted by laminating a dry film.
As shown in FIG. 10C, a plurality of rows 26 are arranged in parallel and the resist film 40 is subjected to exposure of mask pattern through a photo mask 42. A multiplicity of asymmetrical and non-parallel rail patterns are formed on the photo mask 42. The exposure employs, for example, g-line light beam from mercury lamp, and is conducted simultaneously on a multiplicity of slider patterns. This process requires a complex alignment before exposure, and used to take, for example, 10 minutes for one exposure.
As shown in FIG. 10D, resist film on each row 26 is developed. Resist mask pattern 40a is formed thereby.
As shown in FIG. 10E, the ABS 28 of each row 26 is etched by the ion beam through the mask pattern 40a which serves as an etching mask. The portions of the surface of the row 26 not masked are etched to form recessed portions.
Thereafter, the mask pattern 40a is removed and each slider chip is severed from the row 26. Thus, a magnetic head 38 having asymmetrical and non-parallel rails 34 and 36, as shown in FIG. 10F, is formed.
The use of a magnetic head thus formed is determined by the shapes of ABSs on the rails. Namely, denoting both sides of a magnetic disk with which the magnetic head is to be used as side A and side B, the use of the head on side A or side B is preliminarily determined according to the pattern of the rail.
In a magnetic head used on side A of the magnetic disk, the magnetic head fails when one of the magnetic transducers to be used as the side A transducer is not good. In this case, even when the other magnetic transducer to be used as the side B transducer is good, the head is still considered failed, since the pattern of the rails is predetermined to be used on side A.
In the case of parallel rail pattern, as shown in FIG. 6A, one of the magnetic transducers can substitute for the other magnetic transducer that is failed. In the case of asymmetrical and non-parallel rail patterns, it is impossible to substitute in the event of failure of one of the transducers because the design predetermines which side, i.e. outer or inner side, of transducers is used on the magnetic disk.